Glycolysis, Krebs Cycle, and Electron Transport System

A review for the confused (like me!)

Regina Lamendella

AP Biology

December 16, 2008

What is happening while you ingest donuts??

Doughnut = glucose = electrons

= Electrons

What is the purpose of glycolysis and cellular respiration?

Overview Video

• Write down the major “take home messages” from the video

Glycolysis

• 10-STEP reaction10-STEP reaction• (Rxns 1-5) Glucose is phosphorylated and (Rxns 1-5) Glucose is phosphorylated and

cleaved to yield 2 molecules of triose cleaved to yield 2 molecules of triose glyceraldehyde-3-phosphate. glyceraldehyde-3-phosphate. This process uses This process uses two ATPs.two ATPs.

• (Rxns 6-10): The molecules of glyceraldehyde-3-(Rxns 6-10): The molecules of glyceraldehyde-3-phosphate are converted to phosphate are converted to pyruvatepyruvate, with , with concomitant generation of concomitant generation of four ATPs and two four ATPs and two NADH NADH per glucose. per glucose.

• How many net ATPs?How many net ATPs?

GlycolysisGlycolysis

• Where are we within Where are we within the cell?the cell?

• What does ATP What does ATP stand for?stand for?

• What does NAD What does NAD stand for? stand for?

• How many carbons How many carbons does pyruvate have?does pyruvate have?

2 NAD+

1 ATP

1 ATP

Adenosine Tri-PhosphateAdenosine Tri-Phosphate

Nicotinamide Adenine Dinucleotide

Nicotinamide Adenine Dinucleotide H

H

Overall reaction for glycolysis

Glucose + 2 NAD+ + 2 ADP + 2 Pi Glucose + 2 NAD+ + 2 ADP + 2 Pi 2 NADH + 2 pyruvate + 2 ATP2 NADH + 2 pyruvate + 2 ATP

Where do the pyruvate go next?Where do the pyruvate go next?

Intermediary Reaction

• Pyruvate (3-Carbon)Pyruvate (3-Carbon) Acetyl (2-Carbon)-CoA Acetyl (2-Carbon)-CoA• 2 Pyruvate + 2 CoA + 2 NAD2 Pyruvate + 2 CoA + 2 NAD++

22 Acetyl-CoA + 2 COAcetyl-CoA + 2 CO22 + 2 NADH + 2 NADH

Overall energy production so far…Overall energy production so far…

• Glycolysis: Glycolysis: 2 ATP, 2 NADH2 ATP, 2 NADH

• Intermediate reaction: Intermediate reaction: 2 NADH2 NADH

Kreb’s CycleKreb’s Cycle• Roles of the Krebs cycleRoles of the Krebs cycle

– Generate energy by oxidizingGenerate energy by oxidizing acetyl-CoAacetyl-CoA to carbon dioxide and to carbon dioxide and waterwater

– Supply biochemical intermediates for other pathwaysSupply biochemical intermediates for other pathways– Entry point of various degradative pathways for energy Entry point of various degradative pathways for energy

generationgeneration

Squeezing the energy Squeezing the energy out of acetyl-CoA!!!out of acetyl-CoA!!!

acetyl-CoAacetyl-CoA

Krebs Cycle

• Where are we?Where are we?

• What is ATP?What is ATP?

• What is NAD?What is NAD?

• What is FAD?What is FAD?

• How much energy How much energy is produced?is produced?

FADFADH2Flavin Adenine Dinucleotide

H

H

Energy Production from Krebs CycleEnergy Production from Krebs Cycle

Acetyl-CoA + 3 NADAcetyl-CoA + 3 NAD++ + ADP + P + ADP + Pii → →

3 NADH + ATP + 2 CO3 NADH + ATP + 2 CO22

Wait we had two pyruvates to start… have to multiply above by 2!!Wait we had two pyruvates to start… have to multiply above by 2!!

2 Acetyl-CoA + 6 NAD2 Acetyl-CoA + 6 NAD++ + 2 ADP + 2P + 2 ADP + 2Pii → →

6 NADH + 2 ATP + 4 CO6 NADH + 2 ATP + 4 CO2 2

Energy Production So far…

• Glycolysis: 2ATP, 2 NADHGlycolysis: 2ATP, 2 NADH

• Intermediate Step: 2 NADHIntermediate Step: 2 NADH

• Kreb’s Cycle: 2 ATP, 6 NADH, 2 FADHKreb’s Cycle: 2 ATP, 6 NADH, 2 FADH22

• Where to next?Where to next?

Electron Transport System VideoElectron Transport System Video

• Take notes and write down main points.

Electron Transport SystemElectron Transport System• Electron transport chains are redox reactions that transfer electrons from an

electron donor to an electron acceptor.

• The transfer of electrons is coupled to the translocation of protons across a membrane, producing a proton gradient. The proton gradient is used to produce useful work.

NADH= 3 ATPNADH= 3 ATP

FADH2= 2 ATPFADH2= 2 ATP

Total energy production after Total energy production after ETCETC

• Glycolysis:Glycolysis: 2ATP 2ATP; ; 2 NADH= 6 ATP2 NADH= 6 ATP

• Intermediate step: Intermediate step: 2 NADH= 6 ATP2 NADH= 6 ATP

• Krebs: Krebs: 2 ATP2 ATP; ; 6 NADH =18 ATP6 NADH =18 ATP; ; 22 FADHFADH2 2 = 4 ATP= 4 ATP

• 34 ATP from ETC34 ATP from ETC

• 2 ATP from Glycolysis2 ATP from Glycolysis

• 2 ATP from Kreb’s directly2 ATP from Kreb’s directly

• Total ATP production= 38 ATPTotal ATP production= 38 ATP